[Decrease in the serum level of the C3 complement component in noninsulin dependent diabetes of recent onset].

Complement components C3, C4 and C3A were measured by immuno-diffusion in plasma of 36 recent onset insulin-dependent diabetics (IDD) and compared to plasma complement levels of 19 long-standing IDD and 18 non diabetic controls. A significant decrease of C3 and a mild increase of C3A was found in recent-onset diabetes group. However these variations could not be correlated with IgG-islet cell antibodies, C3--fixing islet cell antibodies or A--B HLA antigens. No significant difference was found between long-standing IDD and controls for the 3 complement components. In conclusion, the decrease of C3, found in 30% of recent onset IDD, might be due to increase complement consumption either by the insulitis process or by circulating immune complexes.